150 VIGNETTES FROM INVISIBLE LIFE. 



city. It is so fine and transparent that under 

 the microscope the river, bearing on its bosom the 

 refuse of the city, and also minute objects on the 

 other side of the tubular structure, are readily seen 

 through it. The power which raises and sustains 

 this funnel is astonishing, when the invisible 

 agencies are considered. This filmy structure, 

 distended to its utmost length and kept in position, 

 with its tubular sides almost rigid, so as to allow a 

 free and unimpeded passage to the rushing current 

 of water and refuse from the internal cavities, 

 requires such an amount of muscular force as to 

 excite our utmost wonder. It is also under 

 perfect control, and is contracted and expanded 

 at will ; and in the presence of danger both it 

 and the pores are temporarily closed by the in- 

 habitants beneath. Draw off the water suddenly, 

 and this distended osculum falls over, and is raised 

 again after considerable time and labour with ap- 

 parent difficulty. 



Like most of the lower forms of life the Sponge 

 has several methods of reproducing and propagating 

 its kind. One of these is by a process somewhat 

 analogous to that which is adopted in the vegetable 



